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At least 559 records · Page 31Linked to original sources
PubMed1993

Prediction of the size of unerupted canines and premolars in a Saudi Arab population.

The estimation of the size of unerupted permanent teeth is an essential aspect in treatment planning in the mixed dentition. The commonly used prediction methods of Moyers and Tanaka and Johnston are based on data from a sample of children of Northern European descent. The accuracy of these methods when applied to a different population is questionable. When we applied the Moyers probability tables to a limited sample of a Saudi Arab population, we found that the 35% level was a more accurate determinant than the commonly used 75% confidence level. Likewise, the prediction equations of Tanaka and Johnston overestimated the size of buccal segments in this population. The data illustrate the limitations of these methods when applied to a sample population of other than European descent. From this data, two linear regression equations were developed for tooth size prediction in Saudi Arab children.

Adolescent↗
PubMed1990

Late lower arch crowding: the effect of second molar extraction.

Mesial drift and change in crowding over a 5-year period were compared in 30 subjects whose lower second molars were extracted between ages 11 and 17 years and 30 subjects whose lower second molars were not extracted. Significant differences were found. The nonextraction subjects showed an average forward movement of first molars and an increase in crowding. The extraction group showed slight distal movement of first molars and a decrease in crowding. It is concluded that lower second molar extraction reduces the tendency to forward movement of buccal segments and increased crowding by relieving eruptive pressure from third molars and that the presence of a developing lower third molar with insufficient space can be one cause of late lower arch crowding.

Adolescent↗
PubMed1991

Dynamics of tissue changes found after mechanical loading of the rat incisor. I. A three-dimensional longitudinal study of the morphologic aspects.

A three-dimensional morphometric method was used to evaluate progressive changes in shape and size of recovering dental and periodontal tissues after orthodontic loading. In 35 female rats weighing 212 +/- 4 gm, loads of 19.7 +/- 1.6 gm generated by closed-coil springs were applied for 2 weeks to the shortened lower left incisor. The rats were killed in groups of five at 0, 1, 3, 5, 7, 9, and 10 weeks (groups 0-w to 10-w) after the springs were removed. A group of rats with normal incisors (group C-1) and one with five incisors that had been continually shortened for 10 weeks (group C-2) served as controls for groups 0-w and 10-w, respectively. Width, area, and volume of the tooth and enamel-bordering periodontal ligament (e-PDL) and cementum-bordering PDL (c-PDL) were measured. After 2 weeks of loading (group 0-w), the volume of the compressed e-PDL had decreased by 22%, and the volume of the stretched c-PDL had increased by 72%, suggesting that bone apposition lags behind the rate of tooth movement. During the recovery period, the dental and periodontal parameters tended toward a gradual return to control (C-2) values, although at the end of 10 weeks many still lagged significantly behind the controls. Recovery was slowed by repeated reversals at different sites in the various groups. The ability of the preloaded incisor to adjust to changes in occlusal function was lastingly impaired.

Animals↗
PubMed1990

Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics.

Control of faciolingual tooth inclinations is obtained by using rectangular wire with third-order bends and standard edgewise brackets or by using a straight wire in a preadjusted appliance system. Ideal faciolingual inclinations have been determined previously by measuring facial surface contours relative to coronal long axes. This study evaluates faciolingual inclinations based on occlusal table inclinations relative to occlusal planes. The samples compared include untreated ideal occlusions and malocclusions in three different vertical skeletal growth patterns. Faciolingual inclinations of first molars and central incisors were measured relative to the occlusal plane and to selected cephalometric angular measurements. Statistical comparisons between groups revealed significant differences in the inclinations of the upper incisor relative to the occlusal plane (U1-OP) and the inclination of the occlusal plane relative to sella nasion (OP-SN). No statistically significant intergroup differences were found in the inclination of the lower incisor relative to the occlusal plane (L1-OP) or in the faciolingual inclinations of the maxillary and mandibular first molars. On the basis of the large intergroup differences in the mean angle between the occlusal plane and sella nasion (OP-SN), the use of straight-wire appliance therapy is discussed in terms of the potential for creating differential moments. Because differential moments may facilitate or hinder treatment goals, the practitioner must know the biomechanical sequelae resulting from occlusal plane-sella nasion variations, which differ from normative values when preadjusted brackets are used.

Adolescent↗
PubMed1991

Surgically assisted palatal expansion: an important consideration in adult treatment.

An increasing percentage of orthodontic patients are adults with challenging malocclusions. While some aspects of many adult cases are similar to those seen in children, others must be addressed quite differently. Although many adults appear to be generally more cooperative than children in dealing with the inconveniences of orthodontic treatment, they nonetheless require efficient, less lengthy treatment plans. Many are intolerant of multiple extractions or elaborate surgery. Consequently, the need for practical treatment plans that assure good, stable results is real. Also, any perceived change in the soft tissue profile (positive or negative) is likely to be significant to the patient. The case presented here, in which surgically assisted palatal expansion and extraction of one mandibular incisor were employed, illustrates an approach to a difficult adult orthodontic problem that is both practical and efficient from diagnostic and biomechanical points of view. In this case, in which an adult patient exhibited significant transverse discrepancies and dental crowding, a treatment plan that addressed these considerations was employed.

Adult↗
PubMed1994

Facial and dental changes in adulthood.

The purpose of this longitudinal investigation was to study the dentofacial changes occurring between 25 and 46 years of age in an untreated normal sample. Measurements were made from cephalograms and dental casts available on 15 women and 15 men at age 25 and 46 years. The findings indicate that females exhibited significant increases in all skeletal facial linear dimensions, a decrease in cranial base angle and mandibular prominence, an increase in skeletal convexity and facial divergence. Most of these changes were of relatively small magnitude. Over the span of the study, significant crowding occurred in the mandibular arch. Males exhibited similar significant increases in all skeletal linear dimensions, a decrease in cranial base angle, and increases in maxillary skeletal prominence and skeletal convexity. Increased crowding with age was seen in both maxillary and mandibular arches. In conclusion, the findings indicate that a clinically significant increase in tooth size-arch length discrepancies occurred between 25 and 46 years of age. These changes should be considered as part of the normal "maturational" process. Furthermore, the relative changes in the position of the lips, nose, and chin, cause the lips to appear more retrusive at 46 years of age. These changes should be taken into consideration when orthodontists are considering various treatment and retention options for their adult patients.

Adult↗
PubMed1994

A radiographic study of posterior apical root resorption in orthodontic patients.

The purpose of this study was to determine the extent of apical root resorption, after fixed appliance therapy, in the posterior part of the dentition, and to evaluate if predisposing factors can be pointed out retrospectively. Tooth length in the posterior part of the dentition was measured on pretreatment and posttreatment orthopantomograms of 153 patients who were treated with standard edgewise appliances. Pretreatment and posttreatment tooth lengths were determined, and an attempt was made to explain the differences by sex, age, stage of root formation at onset of orthodontic treatment, extraction versus nonextraction therapy and treatment duration. Patients were divided into two groups according to their root formation. Group A consisted of patients with incompleted root formation at onset of orthodontic treatment except for the first molars. Group B consisted of patients where root formation was completed with the exception of second and third molars. Posttreatment tooth lengths of groups A and B were compared with pretreatment tooth lengths of group B with a paired t test, and correlations with the variables were calculated with multiple regression analysis only in group B. Posttreatment group A showed no significant differences with the mean root lengths of pretreatment group B. Differences between the mean pretreatment and posttreatment root lengths in group B were significant. Posterior teeth showed root shortening during active orthodontic treatment independent of sex, age, extraction versus nonextraction therapy, and duration of active treatment. Teeth with incompleted root formation at onset of orthodontic treatment showed root lengthening during active treatment, yet did not reach their "normal" tooth length.

Adolescent↗
PubMed1995

Changes in tooth size-arch length relationships from the deciduous to the permanent dentition: a longitudinal study.

The purpose of this investigation is to determine the changes in the maxillary and mandibular tooth size-arch length relationship (TSALD) after the complete eruption of the deciduous dentition (mean age = 4.0 years) to the time of eruption of the second molars (mean age = 13.3 years). In addition, an attempt was made to determine whether TSALD in the permanent dentition can be predicted in the deciduous dentition. Records on 35 male and 27 female subjects were evaluated. Each subject had a clinically acceptable occlusion--that is, a normal molar and canine relationship, at the time of eruption of the deciduous and permanent teeth. In addition, each subject had a complete set of data at the two stages of dental development. These selection criteria limited the number of subjects in this investigation to 62. The mesiodistal diameter of all deciduous teeth and their permanent successors, as well as various dental arch width and length parameters, were measured in the deciduous and permanent dentitions. A total of 68 parameters were measured or calculated. Student t tests were used to determine whether significant differences were present between the right and left sides for both male and female subjects. Correlation coefficients r were performed between the deciduous and the corresponding permanent teeth and also for the arch length parameters, as well as TSALD in the two dentitions. Significance was predetermined at the 0.05 level of confidence. Stepwise regression analysis (R2) was used to determine which of the variables in the deciduous dentition could be included in a regression model to determine associations between maxillary and mandibular TSALD in the permanent dentition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Late lower arch crowding: the role of the transverse dimension.

Fifty subjects who were followed longitudinally between 13 and 18 years showed an average increase in lower arch crowding of 2.36 mm. This increase in crowding was examined in relation to tooth width, arch width and jaw width, actual and relative, and to changes in these dimensions with correlation and multiple regression analyses. No relationship was found between width dimensions and late crowding in the lower arch.

Adolescent↗
PubMed1995

Prediction of dental arch development: an assessment of Pont's Index in three human populations.

Pont's Index was established by Pont in 1909 to predict maxillary dental arch width from the sum of the mesiodistal diameters of the four maxillary incisors. The usefulness of Pont's Index is controversial and, as there has been a recent resurgence of interest in its clinical use for establishing dental arch development objectives particularly by nonspecialists, reassessment of the Index in different human populations was considered worthwhile. This study aimed to evaluate Pont's Index in untreated, noncrowded samples of Australian Aborigines (n = 80), Indonesians (N = 60), and white subjects (N = 60). Measurements were obtained directly from plaster casts; they included mesiodistal crown diameters of the four maxillary incisors, as well as intercanine, interpremolar and intermolar maxillary arch widths as specified by Pont. A series of double determinations confirmed the reliability of the method. Considerable individual variability was noted in each population with regard to the difference between observed values and Pont's estimates, ranging from -5.9 mm to +6.2 mm (interpremolar width) and -6.1 mm to +12.7 mm (intermolar width). No person displayed the ideal arch dimensions predicted by the Index, but values were within +/- 1.0 mm for 17.5% of the Indonesian sample, 20.6% of the Aboriginal sample, and 30.8% of the white sample. Dental arch width was generally underestimated by the Index in Indonesians who tended to display relatively small tooth size and large arch width. A more even distribution of estimates was noted in Australian Aborigines and white subjects, with the Aborigines showing large tooth size and broad dental arches, and the white subjects displaying smaller tooth size and narrow arches. Correlation coefficients computed between observed and expected values were low in all three populations studied (range r = 0.01 to r = 0.56). Although the concept of a simple index with predictive ability is very appealing to some clinicians, the results of this study have highlighted the marked variation in values of Pont's Index for persons with apparently good occlusions, representing three different human populations. Tooth size variation was poorly correlated with arch width variation, with persons often being over or under Pont's estimation due to variation in tooth dimension, particularly in the size of the maxillary lateral incisor. It is concluded that Pont's Index is unlikely to be a useful clinical predictor of dental arch width and the index should not be used as a guide to dental arch development in contemporary populations.

Adolescent↗
PubMed1995

Prediction of mesiodistal diameter of unerupted lower canines and premolars using 45 degrees cephalometric radiography.

The reliability of using the oblique cephalometric radiograph for early prediction of the mesiodistal widths of unerupted lower canines and premolars was investigated. Mandibular models and oblique cephalometric radiographs were obtained for 40 Brazilian children (20 boys and 20 girls), in the mixed dentition phase. Further models were obtained for the same sample when all permanent teeth had erupted. A Student t test showed statistically significant differences of tooth size between the sexes but not between right and left sides. Measurements of the unerupted canines and premolars taken from the 45 degrees cephalometric radiograph were statistically greater than the actual values, although a high correlation was observed between them. Linear regression equations and correction tables were established to compensate for this magnification. The actual values for these teeth were compared with the corrected predicted values from the 45 degrees radiograph and with the predicted values obtained from the methods of Ballard and Wylie, Carey, Moyers, and Tanaka and Johnston. A high correlation was observed only between the actual values and the corrected predicted values from the radiograph. The results indicate that, correcting the magnification, the 45 degrees cephalometric radiographic may be used in predicting unerupted lower canine and premolar widths in Brazilian children.

Bicuspid↗
PubMed1996

Prevalence of tooth agenesis and peg-shaped maxillary lateral incisor associated with palatally displaced canine (PDC) anomaly.

Fifty-eight nonsyndromic North American white orthodontic patients with palatal displacement of one or both maxillary canine teeth were studied for associated tooth agenesis and peg-shaped maxillary lateral incisors. Agenesis of permanent teeth was identified by x-ray film analysis. Conical crown-size reduction (peg-shape anomaly) of the maxillary lateral incisor (l2) was determined by direct observation. Increases in absence of third molars and second premolars associated with the palatally displaced canine (PDC) anomaly were statistically very highly significant compared with normative data for tooth-agenesis prevalence. In contrast, the prevalence of l2 agenesis in the PDC sample showed no difference statistically compared with reference values. Reasons for this posterior site-specific suppression of tooth formation are not clear. The l2 peg-shape anomaly exceeded a 10-fold elevation in expression in the PDC sample, a very highly significant increase from normal prevalence. The findings are consistent with a hypothesis that the anomalies of tooth agenesis, tooth-size reduction, and PDC are biologic covariables in a complex of genetically related dental disturbances.

Adolescent↗
PubMed1996

Frequency of Bolton tooth-size discrepancies among orthodontic patients.

The purpose of this study was to determine the percentage of orthodontic patients who present with an interarch tooth-size discrepancy likely to affect treatment planning or results. The Bolton tooth-size discrepancies of 157 patients accepted for treatment in an orthodontic residency program were evaluated for the frequency and the magnitude of deviation from Bolton's mean. Discrepancies outside of 2 SD were considered as potentially significant with regard to treatment planning and treatment results. Although the mean of the sample was nearly identical to that of Bolton's, the range and standard deviation varied considerably with a large percentage of the orthodontic patients having discrepancies outside of Bolton's 2 SD. With such a high frequency of significant discrepancies it would seem prudent to routinely perform a tooth-size analysis and incorporate the findings into orthodontic treatment planning.

Dental Arch↗
PubMed1996

The decision to extract: part II. Analysis of clinicians' stated reasons for extraction.

In a recently reported study, the pretreatment records of each subject in a randomized clinical trial of 148 patients with Class I and Class II malocclusions presenting for orthodontic treatment were evaluated independently by five experienced clinicians (drawn from a panel of 14). The clinicians displayed a higher incidence of agreement with each other than had been expected with respect to the decision as to whether extraction was indicated in each specific case. To improve our understanding of how clinicians made their decisions on whether to extract or not, the records of a subset of 72 subjects randomly selected from the full sample of 148, have now been examined in greater detail. In 21 of these cases, all five clinicians decided to treat without extraction. Among the remaining 51 cases, there were 202 decisions to extract (31 unanimous decision cases and 20 split decision cases). The clinicians cited a total of 469 reasons to support these decisions. Crowding was cited as the first reason in 49% of decisions to extract, followed by incisor protrusion (14%), need for profile correction (8%), Class II severity (5%), and achievement of a stable result (5%). When all the reasons for extraction in each clinician's decision were considered as a group, crowding was cited in 73% of decisions, incisor protrusion in 35%, need for profile correction in 27%, Class II severity in 15% and posttreatment stability in 9%. Tooth size anomalies, midline deviations, reduced growth potential, severity of overjet, maintenance of existing profile, desire to close the bite, periodontal problems, and anticipation of poor cooperation accounted collectively for 12% of the first reasons and were mentioned in 54% of the decisions, implying that these considerations play a consequential, if secondary, role in the decision-making process. All other reasons taken together were mentioned in fewer than 20% of cases. In this sample at least, clinicians focused heavily on appearance-related factors that are qualitatively determinable by physical examination of the surface structures of the face and teeth. They appear to have made primary use of indicators available on study casts and facial photographs and relatively little use of information that is available only on cephalograms or that involves the application of specialized orthodontic theories.

Adolescent↗
PubMed1996

An evaluation of root resorption incident to orthodontic intrusion.

A new radiographic method was developed for measuring changes in root length. With this technique, orthodontic intrusion was investigated as a potential cause of apical root resorption of maxillary incisors. The experimental group consisted of 17 patients with excessive overbite who were treated with a Burstone-type intrusion arch, which delivered a low level of force (about 15 gm per tooth). A control group was made up of 17 patients in full-arch fixed appliances who were randomly selected. After a period of approximately 4 months, the intrusion group had only slightly more root resorption than the controls, 0.6 mm versus 0.2 mm (statistically significant difference). Intrusion measured at the center of resistance of the central incisor averaged 1.9 mm. The amount of resorption was not correlated with the amount of intrusion. A weak correlation, r = 0.45, was found between resorption and movement of the apex (i.e., in addition to intrusion, there was often palatal root movement). Results of this study seem to indicate that intrusion with low forces can be effective in reducing overbite while causing only a negligible amount of apical root resorption.

Adolescent↗
PubMed1996

Prediction of coronal size of third molars by factor and multiple regression analyses.

Factor analysis and multiple regression analysis were made to establish a method for the prediction of the unerupted third molar size. The samples were dental casts of 138 adults (69 women and 69 men) who had all their teeth from the central incisor to the third molar, at least in one side of each maxillary and mandibular dentition. Mesiodistal and buccolingual tooth crown sizes were measured with sliding calipers. Five factors were selected from the factor analysis on the tooth crown sizes. Multiple regression analysis with the third molar as the dependent variable was carried out. Independent variables were selected on the basis of the factors obtained from the factor analysis. Two kinds of multiple regression equations were obtained (the first molar was used as an independent variable in one equation and the second molar was used in the other). The accuracy of the prediction was highest when the lateral incisor, the second premolar, and the second molar were used as independent variables in the maxillary dentition, and the central incisor, the first premolar, and the second molar in the mandibular dentition. The mean of the absolute values of the differences between the predicted values and the actual values was 0.5 mm in the maxillary third molar, and 0.42 mm in the mandibular third molar.

Adult↗